Water well surge blocks are used in the field of underground wells and whose purpose is to agitate or otherwise loosen dirt, mud, silt, sand, etc. for dispersing into the water or other liquid. The particles move upward from the bottom of wells going above the surge block where the water containing the loosened particles is cleaned by filtering and removing the particles. The cleaning process may be performed by machines in the wellbore or above ground. Surge blocks find particular use in water wells and ground water monitoring but the principle of agitating the solution remains the same for oil wells, etc. Typically, such plungers use one way valves that permit the one way flow of water upward towards the cleaning means which may be in the well or above ground. The applicant's invention uses a flexible membrane that overlies a perforated cylinder as the one way valve means. The membrane flexes in one direction to allow the water to flow upward and then flexes against the cylinder to prevent water flow in the other direction, thus trapping the sediments above the surge block.